Since a laminated glass even when broken by external shocks is less likely to be scattered and thus is excellent in safety, it is in broad use for windowpanes of automobiles, railroad vehicles, aircrafts, vessels, buildings, and the like.
Such laminated glass includes those having an interlayer film for a laminated glass interposed between at least a pair of glass sheets and then uniting them. Usually, a plasticized polyvinyl acetal resin film, an ethylene-vinyl acetate copolymer resin film, an ethylene-acrylic copolymer resin film, a polyurethane resin film, a polyurethane resin film containing sulfur element, a polyvinyl alcohol resin film, and the like are used as the interlayer film for a laminated glass.
As the above-mentioned interlayer film for a laminated glass, patent literature 1 described below discloses an interlayer film comprising 50% to 80% by weight of PVB (acetalized polyvinyl alcohol) and 20% to 50% by weight of a softener. In the interlayer film described in the patent literature 1, 30% to 70% by weight of the softener is polyalkylene glycol or its derivatives represented by the formulae (A1) to (A6) below.HO—(R—O)n—H  (A1)
In the above formula (A1), R is an alkylene group and n is >5.HO—(CH2—CH2—O)n—(CH2—CH(CH3)—O)m—H  (A2)
In the above formula (A2), n is >2, m is >3, and (n+m) is <25.R1O—(CH2—CH2—O)n—(CH2—CH(CH3)—O)m—H  (A3)HO—(CH2—CH2—O)n—(CH2—CH(CH3)O)m—R1  (A4)
In the above formula (A3) or (A4), n is >2, m is >3, (n+m) is <25, and R1 is an organic group.R1—O—(R2—O)n—H  (A5)
In the above formula (A5), R2 is an alkylene group, n is ≧2, and R1 is an organic group.R1—O—(R2—O)n—R3  (A6)
In the above formula (A6), R2 is an alkylene group, n is >5, and R1 and R2 are each an organic group.
In the composite safety glass composed of the interlayer film as mentioned in the patent literature 1, since the above-described specific compound is contained as a softener in a specific ratio as mentioned above, such composite safety glass has excellent sound insulation performance.    Patent Literature 1: WO 01/19747